


hypnotism

by mvrcredi



Series: cap-iron bingo fills [17]
Category: The Avengers (Marvel) - All Media Types
Genre: Alternate Universe - Lifeguards, Alternate Universe - Merpeople, Alternate Universe - Modern Setting, Alternate Universe - No Powers, Alternate Universe - Non-Famous, Alternate Universe - Normal Life, Human Tony Stark, In a sense, M/M, Siren Steve Rogers, Sirens, Stony Bingo, Transformation, True Love's Kiss
Language: English
Status: Completed
Published: 2019-04-23
Updated: 2019-04-23
Packaged: 2020-01-24 10:12:30
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,477
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18569290
Author URL: https://archiveofourown.org/users/mvrcredi/pseuds/mvrcredi
Summary: Tony had sworn it was a person in need of his help. What he hadn't expected was a siren attempting to lure him to his death.





	hypnotism

**Author's Note:**

> fill for my 'au: mermaids/sirens' bingo square.

Tony was carrying out his business on the beach like any other work day.

It was bright, sunny, warm, and plenty people were out in the water. Fortunately, so far it seemed there’d be minimal issues that day. But with water and people, there were so many unexpected things possible.

Just past one o’clock in the afternoon was when Tony spotted his first major issue. Through binoculars, he’d found what looked to be a person in distress, far out from where the recommended swim area was. He had alerted the other lifeguards currently on duty—Clint and Natasha—before heading out on the boat to see what the issue was about.

But when Tony reached the area of the commotion, there was nothing there.

Annoyed by the lack of reason for travelling so far out from shore, he was ready to turn the boat around and head back—but then he spotted _him._

A man was leaning over the side of his boat, arms crossed over one another to hook him into place. He seemed innocent enough, with his wide, blue puppy dog eyes, neatly combed hair, and shy smile.

“Can I help you?” Tony asks.

The man just smiles wider, all lip and no teeth, before he begins singing in a lovely, warm baritone. It was then Tony’s radio crackled to life.

 _“Stark, get out of there!”_ Came the urgent voice of Clint.

Tony responds after a moment, “And why should I? It’s just... it’s so nice. Can you hear it?”

 _“Stark! Listen to me, you have to turn back now,”_ Clint presses more urgently. _“Tony, that’s a siren! Get the fuck out of there before I have to go and drag your ass back to shore.”_

“It’s fine,” Tony dismisses. The singing really was mesmerizing. Hypnotising, almost.

He drops the radio on the seat, finding himself gravitating towards the handsome man serenading him.

The man sings with a smile, leaning closer to Tony. Tony finds himself drawing closer—until he notices the very _inhuman_ tail swishing gently beneath the water. _Huh. So that’s what Barton was talking about._

Tony scrambles backwards, suddenly startled out of his trance. Unfortunately, this angers the siren. The singing comes to an abrupt end, a furious expression settling like kicked up sand from the ocean floor. However, instead of attacking, the siren slowly sinks back into the water until he’s out of sight.

The lifeguard is tempted to peer over the edge to see where he had gone, but decides against it—his first order of business is to start the boat up again.

Tony doesn’t get the time of day though, of course. In a flurry of motion, the siren is launching himself over the side of the boat with impressive force, tackling Tony over to the other side of the boat. He teeters, sending them both back into the water.

Therein, Tony gets a first, up-close-and-personal look of the innocent-face-turned-creature-from-hell. The siren’s round pupils had become slits, and rather large fangs were now very visible and very terrifying. His ears were now more fin-like, and his tail was now wrapped tightly around Tony, in a similar fashion to a snake suffocating his prey. Not that he wouldn’t drown otherwise.

Tony was struggling to hold his own, being that it was difficult for a human to do any damage underwater. He was losing this fight, Tony knew that much.

His moments seemed fleeting as they travelled further away from the boat, no closer to the surface.

 _Why don’t you just give up?_ A foreign voice in his head tells him. Tony couldn’t exactly respond, except by continuing to fight back weakly.

 _Let me survive, and we’ll get on with our day, alright?_ The voice says, condescending. Tony had never realized sirens lured people into the sea for a reason other than entertainment. Or maybe they did, who knew? This siren didn’t exactly seem to be peaceful.

There’s finally a moment where Tony blacks out due to the loss of oxygen. While he’s unconscious, he misses his rescue, as well as the capture of the siren.

 

-=-

 

“Water... please...” a voice— _that_ voice—rasps.

“No, I really don’t think so, buddy,” Tony hears Clint respond, tone cold. “You shoulda thought about that before trying to drown my friend.”

There’s a thump, and what sounded like someone slumping over. The siren doesn’t respond, likely tired and weak from being outside his own environment.

Tony’s eyes flutter open, and he sits up slowly. Clint rushes to his side.

“You alright? Feeling better?”

“I’m fine. Not dead,” Tony shrugs. He peers around Clint, spotting Natasha silently glaring at the siren, who was tied against a post, looking pale and sickly. Tony couldn’t help but feel a _little_ bad.

“Why’d you bring him back?” Tony doesn’t mean to ask the question, but it slips out anyway.

Natasha turns her attention to Tony. “Didn’t want him to hurt any patrons.”

“Yeah, but don’t you think _killing_ him is a little, I don’t know... immoral?”

“He almost killed _you!”_ Clint exclaims, appalled.

Tony ducks his head, hunching his shoulders. Quietly, he argues, “But... he didn’t.”

Clint nearly shouts, “Because I had to go out and get you! Because you didn’t listen to my warnings and instead nearly drowned! Because you’re an idiot!”

“It looked like he needed help from afar!” Tony retaliates. Natasha remains silent—the argument really was pointless. Tony _was_ still alive, and that was that.

In his peripherals, Tony spots movement from the siren. The blond rolls his head, expression showing he was clearly in pain, suffering. The siren’s less vibrant blue tail flickers, as if he’s trying to reach something. Then Tony sees the water bottle placed a taunting distance away. He raised an eyebrow at it—now _that_ was a bit cruel. Not only depriving the siren of water, but having it at the ready just out of reach.

Tony slides off the cot, making a beeline for the bottle. He takes it and hesitantly offers it to the siren.

Despite the obvious need for it, the blond hisses, fangs and constricting pupils making a reappearance. He looks offended by the offer, but Tony could also see the internal conflict.

Tony retracts the bottle when the siren hisses, causing the latter to look almost regretful. Clint and Natasha watch the exchange wordlessly.

“No,” Tony scolds. “No water unless you behave.”

The siren stays silent, eyeing the bottle. He listens to Tony, though. He doesn’t make another move to attempt to ward off Tony.

“Good,” Tony praises. He felt like he was talking to a misbehaving child. “Can you tell me your name?”

The siren looks to Tony, wary. For a moment, Tony doesn’t think he’ll give him an answer, but eventually the siren supplies in a small voice, “Steven.”

Tony turns back to his friends, and fellow lifeguards for a second. They all share a look, each taken aback at Tony’s ability to get across—without conflict—to the siren. Or, Steven, he guessed.

“Okay. Alright,” Tony nods to himself. “Okay. Steven. Um. If I... if I untie you, to give you this water, you have to promise you won’t attack me, or anyone else. Not that this is a lot to get by, but we’ll get you something better. Later. If you promise. Me. Us. Yeah.”

Tony isn’t quite sure why he was so nervous. He’d talked to plenty of children and patrons in need of first aid (which were a lot harder to talk to than normal, healthy adults), and land was his domain. He could easily overpower Steven here.

Steven weighs his options, before nodding slowly. Tony places the water bottle down carefully, moving to undo the ropes tied around the siren.

Tony senses Steven is holding himself back from attacking, knowing he needed the water, even if it was such a small amount. He had reached a point of desperation.

The lifeguard unscrews the cap and pushes the bottle forward. It was like making contact with a wild animal—though he supposed that wasn’t all that far off. Tony, Clint, and Natasha watch with baited breath, to see what the siren would do.

Steve pulls the water bottle towards himself with his tail, cradling the drink like at any moment it would be taken from him, with or without him stepping out of line.

The three lifeguards watch the water be consumed in a matter of seconds, like a breath of fresh air after being underwater for so long. Tony imagines it’s exactly like that for the siren.

A pale pink tinge returns to Steven’s face, but he still appears weak, sickly. He was likely drying out—he likely needed to be _submerged_ in water to be rejuvenated.

“What do we do now?” Clint asks, cutting through the silence.

Tony shrugs helplessly. “Get him _in_ some water, I guess.”

Steven looks appreciative of the suggestion, Tony notes. Tony nods to his friends, glancing between them and the siren. “Yeah, more water.”

“We can’t just release him back with the patrons,” Clint says.

“I know that, dumbass,” Tony rolls his eyes. “But where?”

They all ponder a moment before Natasha asks, “You have a pool, right Stark?”

“I—yeah.”

“Is it salt water?”

“Mm hm. Why do you—oh no. No, no, no. I’m not—I’m not keeping a _siren_ in my backyard. How would I explain that to Rhodey? Pepper? Literally _anybody_ I have over?” Tony was very opposed to the suggestion, but a voice in the back of his mind was telling him it was really the only... better solution. It was either release Steven back into the ocean and let him terrorize more people, let him shrivel up and die, send him to some zoo or lab where someone could contain him, or keep him in Tony’s pool.

Natasha and Clint look sympathetic, and Tony sighs in defeat.

“Fine. But how are we getting him there without being spotted?”

 

-=-

 

As it turned out, transporting a siren without being made was rather difficult.

Tony’s car was barely big enough to contain Steven’s tail, and the siren wasn’t having a very easy time manoeuvring himself around. This time, he wasn’t trying to be difficult—Steven was genuinely struggling.

But, despite the challenge, they eventually made it to Tony’s home. They struggled more to get Steven to the pool, but when he was finally dropped in, the siren became more... alive.

Tony watched briefly as Steven relished in the water, before turning his back to go on and do other things.

Dealing with a siren was not what he expected when he became a lifeguard.

It only occurred to Tony several hours later that Steve probably required more than just water to survive.

He finds himself sitting on the edge of the pool late that night, his legs, almost up to his knees, dipped in the water. Steve is looking up at him questioningly.

“You actually _eat,_ don’t you?”

Steven nods, bobbing gently in the water, tail swaying below the surface.

“Not much of a talker, huh?” Tony sighs. “What do you eat then?”

“Human,” Steven grins, before adding softly, “Fish.”

“Like, raw?”

Steven nods again. Tony supposed the most he’d get out of the blond was the singing that nearly led to his death, that damn voice in his head as water filled his lungs, and the occasional few-worded answers.

Ton stands, pulling his legs from the pool. “I’ll be back. Stay put.”

 

-=-

 

“What in the—Tony, who— _what_ is that?” Pepper screams upon spotting Steven in the pool.

“Hm? Oh! That’s Steven,” Tony explains nonchalantly, as if it’s nothing out of the ordinary.

“What’s the—the tail. What?” She sputters.

“He’s a siren, Pep. He actually tried to kill me, and probably would have if it weren’t for Clint, but whatever,” Tony shrugs. “I’m keeping him here now until we figure out what to do in the long run.”

“Why would you do that?! Tony, you idiot!”

“Huh. Clint said that too.”

“And rightfully so!” Pepper stresses. She freezes suddenly. “Oh. Oh my god. It’s waving at me.”

Tony hums. “ _He._ And his name is _Steven._ I told you already. Also, turns out he’s not as bad when you’re not currently his prey. Did you know he’s an artist?”

“An artist,” Pepper scoffs exasperatedly. “A siren that’s an artist. Unbelievable. You are—this is unbelievable.”

Tony rolls his eyes. “Go make conversation or something. He won’t hurt you—he knows the consequences if he does.”

“You’re treating him like a pet, Tony!”

“So now you’re taking his side?”

“If I’m completely honest, I don’t know where I stand on this,” Pepper massages her temples. “This is so weird. My best friend is keeping the creature that almost killed him in his pool. My best friend is taking _care_ of the creature that almost killed him that’s in his pool. I’ve gone insane, haven’t I?”

“Don’t worry Pepper,” Tony consoles. “You’re not the one that’s gone insane.”

“It’s probably from all that sun you get,” she shakes her head. “You should get an indoor job. Maybe that way you wouldn’t also get _attacked by sirens!”_

“This is the only time that’s happened!”

“And who’s to say it won’t happen again?” Pepper argues. “Then what will you do? Bring that siren home too? And what if they’re territorial or something? What if they kill each other? God, Tony. You’ve created a mess.”

“I didn’t start it,” Tony pouts.

 

-=-

 

 “... Did you know it’s possible for sirens to become human?”

Tony furrows his brows, readjusting his crossed legs. “You can? How?”

Steven smiles vaguely, but doesn’t respond. Instead, he jerks his chin towards something behind Tony, before slinking away back into the water. Tony is confused, but turns around anyway. Rhodey was in the house, unaware of Steven. So far, at least.

Tony rushes to greet him before he notices Steven. He knew his friends oftentimes let themselves into his house to go swimming, but that wasn’t exactly an option as of now.

“Hey, Rhodey,” Tony says as he steps inside, dragging out each word. “I’m afraid the pool’s out of commission today. We could go to the beach though! Or something.”

“What are you hiding from me?”

“Nothing!” Tony exclaims, stepping in the way of Rhodes’ view when he tries to peer out the window. “Nothing at all. Beach is nicer anyway.”

“Yeah, but the beach is crowded,” Rhodey looks unimpressed. “Seriously, Tones. What is it?”

Tony huffs. _“Ihaveasirenlivinginmypool.”_

Rhodes takes a moment to register what Tony had said, before shouting, “A siren?! Tony! What the fuck, man? _Why_ the fuck?”

“Okay, look,” Tony drops his shoulders. “We didn’t want him out near the patrons, and we didn’t really have anywhere else to put him.”

“How did you even get him in the first place?”

“Oh! That,” Tony laughs humourlessly. “He tried to kill me. But! Before you start yelling at me—he didn’t. Alright? And he’s... not so bad. Also, apparently! Apparently—sirens can become humans. Fun fact, huh?”

Rhodey shakes his head. “You know what? Whatever. You’ve been in weirder situations before. Albeit purely human situations. But still.”

“Fair enough,” Tony pauses. “You wanna meet him?”

“Not really, no,” Rhodey replies bluntly. “I’m going home. You have fun with your siren friend.”

Rhodes tosses his towel over his shoulder before turning and heading towards the front door without hesitance.

“Rhodey, wait! I’m not—he’s not my,” the door slams shut, “friend.”

Tony sighs, slumping his shoulders. He really needed to figure out what to do with the siren living in his pool. Steven was a problem.

Tony goes back out to the yard to find Steven back in the same position he was before Rhodey’s interruption. His arms are folded over the edge of the pool, his chin resting on his arms. His eyes follow Tony as he nears.

Tony drops cross-legged in front of Steve. “You mentioned something about becoming human?”

Steven nods once. “I did, yes.”

“Care to elaborate?” Tony asks. Really, he _was_ curious.

“Hm,” Steven purses his lips, pausing for effect. “I don’t know. Do I?”

Tony rolls his eyes, bracing himself to get up and leave. “Remind me not to ask you any serious questions any more. Or any siren, for that matter. Actually, come to think of it, why don’t I just drop you off at an aquarium, huh?”

Steven pales, barely, shaking his head almost unnoticeably. In a quiet voice he says, “Please don’t.”

In an instant, Tony softens and relaxes back onto the stone that surrounds the pool. “Hey, I’m sorry,” he consoles. “I didn’t mean it.”

Steven sighs, sinking further into the water. “I’m just—I’ll explain another time,” he tells Tony before completely submerging himself and swimming away. Tony watches him circle the pool for a bit before getting up. He can’t imagine Steven enjoys being cramped up in such a small space in comparison to the ocean. He’d find a solution soon.

 

-=-

 

“I had a friend who—he was put into an aquarium,” Steven blurts one day, and it takes Tony a moment to realize why he’s suddenly bringing up something that seemed sensitive. It was _extremely_ unusual for Steven to indulge him with some personal story.

Tony says nothing, and in turn Steven continues. “Some fisherman caught him. Kept him trapped. Gave him to an aquarium because they thought they would profit,” he explains, a distant look in his normally fierce gaze.

“Oh, Steven—“

“No, don’t,” Steven interjects, growling. “I don’t need your pity.”

“That’s not—“

Steven sends him a cold glare, and Tony puts his arms up in surrender. Steven dives back into his story. “Before you interrupted, I was going to tell you he got out. He was causing so much trouble and costing so much of your human currency that he was dumped back into the ocean. Except, minus an arm. It had initially gotten injured in the fishermen’s net, but later severed in his tank. Got caught on something. He couldn’t preform, or whatever, so they just cut it off. Amputated it. It could have been saved, but those cheap bastards...”

“I really am sorry, Steven,” Tony whispers. “And this isn’t pity.”

“Then what is it?” Steven sneers.

“Consolation,” Tony replies. “I do feel bad for you because that’s an awful thing, but I’m offering comfort. I know you’re strong, but sometimes people need somewhere to reach out and vent. And that’s what I’m giving you.”

“I—“ Steven searches Tony’s face for any sort of... sign of anything else. “Thank you.”

“You’re welcome.”

The words are simple, really, but Tony feels like they hold an odd amount of weight to them. They settle into silence that’s not comfortable, but nor is it uncomfortable. Steven’s tail bobs gently in the water as he stares blankly ahead. Tony leans back on his hands, tilting his head back and closing his eyes to soak in the rays of the sun.

“Tony, about the, um. Human thing.”

Tony snaps his eyes open, immediately intrigued. “What about it?”

“I—it’s,” Steven takes a deep breath. “It sounds dumb, cliché, but I—the only way I can become _human_ is through, uh. True love?”

“You say that like it’s a question.”

“Are you skeptical?”

“Maybe!” Tony laughs humourlessly. “First, the story. I can deal with one serious thing, but two?! This is hardly like you! ‘Course I’m a bit... in doubt.”

Steven looks irritated. “Are you insinuating that I can’t be serious?”

“No, no, that’s not—that’s not what I meant,” Tony sighs. “I just... normally you’re so _flippant_ when it comes to serious questions. And you’re rather evasive when I wonder about anything more than your age and what sirens eat other than people. Even then."

Steven slumps his shoulders. Tony could tell Steven knew exactly what the former was talking about. He looked almost shameful, but not quite. Not quite.

“I wasn’t sure I could trust you,” Steven admits. Tony scoffs, but Steven amends, “But I do know now, Tony. I can. Trust you.”

“Alright then. You’ve forced my hand,” Tony chews his bottom lip. “So, say this whole “needing true love to become human” thing is real, how could you tell? Could you stop it if you wanted to?” Tony wants to ask more, but he cuts himself off in fear he had already gone too far.

Steven shrugs. “I couldn’t stop it. That’s how I would tell; it would just happen, likely with a physical connection. Maybe a kiss. It’s really not often a human _really, truly_ falls in love with a siren,” he explains. “Usually, there’s no time for a siren and human to build a relationship of any sort.”

“Fair,” Tony agrees. A siren’s whole shtick was serenading a human into the deep, blue depths of the ocean to drown—and eat—them. Tony ventures to ask another question. “Would you be human forever, then?”

“I don’t... I don’t know, actually,” Steven furrows his brow. “I’ve heard of some being able to completely change back and forth, others remaining physically human but sharing some traits with that of their former siren-self. A few staying human, through and through. I think it could depend on the siren, maybe. On something, at least. Or maybe some of those stories are simply false. I wouldn’t know.”

“You haven’t met anyone who had had a human truly fall in love with them before?” Tony questions. He’s finding that this seems the best time to ask Steven questions, while he’s being less playful and avoidant.

“I haven’t, no,” Steven shakes his head. After, it’s almost like a switch flicks in Steven’s behaviour. “But it doesn’t matter, does it? I doubt I’m finding true love any time soon. Not with this unfortunate restriction,” Steven grins glibly, gesturing to the pool. He looks sad.

“Well, it wouldn’t hurt to try, would it?”

Steven freezes, mostly confused Tony would assume. “Sorry?”

“True love. A kiss, or what have you,” Tony clarifies. “Would it hurt to try?”

“Are you saying you love me?” Steven asks him an impossibly small voice. His tone is tangled with uncertainty, fear, hurt. He sounds so doubtful, like his heart had been broken before. Or perhaps it was only self-loathing and what insecurities that had built up over hearing hundreds of stories about “those terrible, terrible sirens.”

Tony refuses to looks Steven in the eyes. “I think... I think I do.”

Steven doesn’t answer him.

“This past while of getting to know you, spending so much time with you—I think I’ve fallen pretty hard,” Tony chuckles rather self-deprecatingly. “So why not give it a shot?”

It feels like an eternity before Steven responds with a single, but hopeful word: “Okay.”

Tony smiles, moving to sit on his knees. He ignores the scraping feeling at his shins against the cement, concentrated on his goal.

He leans down, Steven pushing himself out of the water to meet Tony in the middle. The kiss is soft and sweet and gentle and slow. It’s perfect.

They separate when they decide it’s time to breathe. However, nothing happened short of their kiss.

Steven seems almost disappointed. “I thought that would work.”

Tony shrugs helplessly. “I would think so, too. Does the—does the whole love thing have to go both ways, or?”

Steve huffs. “Believe me, it does,” he says, and nothing else.

Tony checks his watch. “Well, I have work soon, so I have to go. We’ll discuss this when I get back, yeah?”

Steven nods solemnly. “Yeah, I guess we will.”

 

-=-

 

“Oh, Jesus _Christ!”_ Tony screams the _second_ he walks out into his backyard.

There sits Steven in one of his lounge chairs, except this time more human, and, well... more _naked._ He appeared to have been sunning himself until Tony had arrived.

“Oh, Tony, hey!” he calls, and Tony is too stuck in his own stupor to move any closer. His feet feel glued to the ground as he stares at the devilishly handsome specimen. Steven was always handsome, sure, but _man_ those legs were great. And a few certain other things. _Thing._

“Steven, hey,” Tony squeaks. “You’re, um. Human.”

“Yeah, I am!” Steven beams. “I guess there’s just a delay in the effects.”

Tony nods. “I guess, yeah. But since you’re human now, _I guess_ we’d also better get you clothed before someone who isn’t me comes along,” Tony beckons for Steven.

“Oh, yes, that would make sense,” Steven agrees. He throws his legs over the side of the chair, ready to stand. He hesitates, however, intently staring at the ground.

“Are you alright, there?”

“Mm hm, just peachy,” Steven throws up a dismissive hand. “I’m, uh. Still a bit new to the whole walking thing, though. If you could—“

“Oh,” Tony pauses for a moment, still trying to register the whole of what was happening before realizing what Steven was asking for. “Oh! Yes, of course! Sorry, let me help you.”

Tony rushes to his aid and helps Steven into the house. He stumbles a bit, but they make it inside without a hitch otherwise. Tony sits Steven down in the first easily-accessible chair in view.

“Right, clothes,” Tony makes a point of saying, mostly to himself. “I’ll be back.”

Tony returns shortly with boxers, jeans, and a shirt that would likely be a tad too small for Steven, but Tony didn’t think he would mind all that much. He tosses the pile at Steven.

“So, the underwear and jeans should fit because I believe they belong to Thor, and he’s a pretty big guy—don’t worry, everything’s clean—and the shirt was the biggest one of mine I could find so sorry if it doesn’t fit. Not that I’d care if you went shirtless. I just—other people might,” Tony rambles.

Steven is only smiling in return. Tony doesn’t think he’s ever seen the siren—or man now, perhaps—so genuinely happy. Tony couldn’t help but smile back in contagion.

“Thank you, Tony. This means a lot,” he ponders, “You mean a lot. And, uh. Sorry for trying to kill you all that time ago.”

Tony waves a hand. “Psh. It’s no problem. It’s in the past now, and we managed to get here, didn’t we?

“We did,” Steven grins.

 

-=-

 

They end up having a hell of a time reintroducing Steven to those who had met him as a siren. Tony keeps photos of all of their reactions. He has a few extra of Clint getting scared by Steven’s whole hissy fang thing. Turns out Steven was lucky enough to have the ability to switch between complete siren and complete human at will, and not just when he hit water as one would think.

Tony taught him the ways of people, the world, and they lived happily—as dumb and cliché as it sounds.

**Author's Note:**

> i really liked this concept?? had fun writing it, at least
> 
> i'd like to know if you enjoyed it! comments and kudos are always greatly appreciated <3


End file.
